Commit 346e15be authored by Jason Baron's avatar Jason Baron Committed by Greg Kroah-Hartman
Browse files

driver core: basic infrastructure for per-module dynamic debug messages 



Base infrastructure to enable per-module debug messages.

I've introduced CONFIG_DYNAMIC_PRINTK_DEBUG, which when enabled centralizes
control of debugging statements on a per-module basis in one /proc file,
currently, <debugfs>/dynamic_printk/modules. When, CONFIG_DYNAMIC_PRINTK_DEBUG,
is not set, debugging statements can still be enabled as before, often by
defining 'DEBUG' for the proper compilation unit. Thus, this patch set has no
affect when CONFIG_DYNAMIC_PRINTK_DEBUG is not set.

The infrastructure currently ties into all pr_debug() and dev_dbg() calls. That
is, if CONFIG_DYNAMIC_PRINTK_DEBUG is set, all pr_debug() and dev_dbg() calls
can be dynamically enabled/disabled on a per-module basis.

Future plans include extending this functionality to subsystems, that define 
their own debug levels and flags.

Usage:

Dynamic debugging is controlled by the debugfs file, 
<debugfs>/dynamic_printk/modules. This file contains a list of the modules that
can be enabled. The format of the file is as follows:

	<module_name> <enabled=0/1>
		.
		.
		.

	<module_name> : Name of the module in which the debug call resides
	<enabled=0/1> : whether the messages are enabled or not

For example:

	snd_hda_intel enabled=0
	fixup enabled=1
	driver enabled=0

Enable a module:

	$echo "set enabled=1 <module_name>" > dynamic_printk/modules

Disable a module:

	$echo "set enabled=0 <module_name>" > dynamic_printk/modules

Enable all modules:

	$echo "set enabled=1 all" > dynamic_printk/modules

Disable all modules:

	$echo "set enabled=0 all" > dynamic_printk/modules

Finally, passing "dynamic_printk" at the command line enables
debugging for all modules. This mode can be turned off via the above
disable command.

[gkh: minor cleanups and tweaks to make the build work quietly]

Signed-off-by: default avatarJason Baron <jbaron@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 33376c1c

Documentation/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -1713,6 +1713,11 @@ and is between 256 and 4096 characters. It is defined in the file 
			autoconfiguration.

			Ranges are in pairs (memory base and size).



	dynamic_printk

			Enables pr_debug()/dev_dbg() calls if

			CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also

			be switched on/off via <debugfs>/dynamic_printk/modules



	print-fatal-signals=

			[KNL] debug: print fatal signals

			print-fatal-signals=1: print segfault info to

include/asm-generic/vmlinux.lds.h

+9 −1
Original line number Diff line number Diff line
@@ -268,7 +268,15 @@ 
	CPU_DISCARD(init.data)						\

	CPU_DISCARD(init.rodata)					\

	MEM_DISCARD(init.data)						\

	MEM_DISCARD(init.rodata)

	MEM_DISCARD(init.rodata)					\

	/* implement dynamic printk debug */				\

	VMLINUX_SYMBOL(__start___verbose_strings) = .;                  \

	*(__verbose_strings)                                            \

	VMLINUX_SYMBOL(__stop___verbose_strings) = .;                   \

	. = ALIGN(8);							\

	VMLINUX_SYMBOL(__start___verbose) = .;                          \

	*(__verbose)                                                    \

	VMLINUX_SYMBOL(__stop___verbose) = .;



#define INIT_TEXT							\

	*(.init.text)							\

include/linux/device.h

+5 −1
Original line number Diff line number Diff line
@@ -550,7 +550,11 @@ extern const char *dev_driver_string(const struct device *dev); 
#define dev_info(dev, format, arg...)		\

	dev_printk(KERN_INFO , dev , format , ## arg)



#ifdef DEBUG

#if defined(CONFIG_DYNAMIC_PRINTK_DEBUG)

#define dev_dbg(dev, format, ...) do { \

	dynamic_dev_dbg(dev, format, ##__VA_ARGS__); \

	} while (0)

#elif defined(DEBUG)

#define dev_dbg(dev, format, arg...)		\

	dev_printk(KERN_DEBUG , dev , format , ## arg)

#else

include/linux/dynamic_printk.h

0 → 100644
+93 −0
Original line number Diff line number Diff line 
#ifndef _DYNAMIC_PRINTK_H

#define _DYNAMIC_PRINTK_H



#define DYNAMIC_DEBUG_HASH_BITS 6

#define DEBUG_HASH_TABLE_SIZE (1 << DYNAMIC_DEBUG_HASH_BITS)



#define TYPE_BOOLEAN 1



#define DYNAMIC_ENABLED_ALL 0

#define DYNAMIC_ENABLED_NONE 1

#define DYNAMIC_ENABLED_SOME 2



extern int dynamic_enabled;



/* dynamic_printk_enabled, and dynamic_printk_enabled2 are bitmasks in which

 * bit n is set to 1 if any modname hashes into the bucket n, 0 otherwise. They

 * use independent hash functions, to reduce the chance of false positives.

 */

extern long long dynamic_printk_enabled;

extern long long dynamic_printk_enabled2;



struct mod_debug {

	char *modname;

	char *logical_modname;

	char *flag_names;

	int type;

	int hash;

	int hash2;

} __attribute__((aligned(8)));



int register_dynamic_debug_module(char *mod_name, int type, char *share_name,

					char *flags, int hash, int hash2);



#if defined(CONFIG_DYNAMIC_PRINTK_DEBUG)

extern int unregister_dynamic_debug_module(char *mod_name);

extern int __dynamic_dbg_enabled_helper(char *modname, int type,

					int value, int hash);



#define __dynamic_dbg_enabled(module, type, value, level, hash)  ({	     \

	int __ret = 0;							     \

	if (unlikely((dynamic_printk_enabled & (1LL << DEBUG_HASH)) &&	     \

			(dynamic_printk_enabled2 & (1LL << DEBUG_HASH2))))   \

			__ret = __dynamic_dbg_enabled_helper(module, type,   \

								value, hash);\

	__ret; })



#define dynamic_pr_debug(fmt, ...) do {					    \

	static char mod_name[]						    \

	__attribute__((section("__verbose_strings")))			    \

	 = KBUILD_MODNAME;						    \

	static struct mod_debug descriptor				    \

	__used								    \

	__attribute__((section("__verbose"), aligned(8))) =		    \

	{ mod_name, mod_name, NULL, TYPE_BOOLEAN, DEBUG_HASH, DEBUG_HASH2 };\

	if (__dynamic_dbg_enabled(KBUILD_MODNAME, TYPE_BOOLEAN,		    \

						0, 0, DEBUG_HASH))	    \

		printk(KERN_DEBUG KBUILD_MODNAME ":" fmt,		    \

				##__VA_ARGS__);				    \

	} while (0)



#define dynamic_dev_dbg(dev, format, ...) do {				    \

	static char mod_name[]						    \

	__attribute__((section("__verbose_strings")))			    \

	 = KBUILD_MODNAME;						    \

	static struct mod_debug descriptor				    \

	__used								    \

	__attribute__((section("__verbose"), aligned(8))) =		    \

	{ mod_name, mod_name, NULL, TYPE_BOOLEAN, DEBUG_HASH, DEBUG_HASH2 };\

	if (__dynamic_dbg_enabled(KBUILD_MODNAME, TYPE_BOOLEAN,		    \

						0, 0, DEBUG_HASH))	    \

			dev_printk(KERN_DEBUG, dev,			    \

					KBUILD_MODNAME ": " format,	    \

					##__VA_ARGS__);			    \

	} while (0)



#else



static inline int unregister_dynamic_debug_module(const char *mod_name)

{

	return 0;

}

static inline int __dynamic_dbg_enabled_helper(char *modname, int type,

						int value, int hash)

{

	return 0;

}



#define __dynamic_dbg_enabled(module, type, value, level, hash)  ({ 0; })

#define dynamic_pr_debug(fmt, ...)  do { } while (0)

#define dynamic_dev_dbg(dev, format, ...)  do { } while (0)

#endif



#endif

include/linux/kernel.h

+6 −1
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/log2.h>

#include <linux/typecheck.h>

#include <linux/ratelimit.h>

#include <linux/dynamic_printk.h>

#include <asm/byteorder.h>

#include <asm/bug.h>
@@ -303,8 +304,12 @@ static inline char *pack_hex_byte(char *buf, u8 byte) 
#define pr_info(fmt, arg...) \

	printk(KERN_INFO fmt, ##arg)



#ifdef DEBUG

/* If you are writing a driver, please use dev_dbg instead */

#if defined(CONFIG_DYNAMIC_PRINTK_DEBUG)

#define pr_debug(fmt, ...) do { \

	dynamic_pr_debug(fmt, ##__VA_ARGS__); \

	} while (0)

#elif defined(DEBUG)

#define pr_debug(fmt, arg...) \

	printk(KERN_DEBUG fmt, ##arg)

#else

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